E-15 will not hurt anything, shoot E- 85 would be fine if you could re-tune for it as e-85 requires more fuel.
That's not correct. E-85 is corrosive as hell and breaks down your rubber components. It does not provide the same cooling internal to the combustion chamber either.
If a vehicle is designed for it, fine, only a few negative issues like less MPG.
If the engine is not flex fuel, E-85 is awful AND E-15 would also be a long term problem.
Just 'cause the red necks doing left turns run ethanol doesn't make it right for a stock vehicle--the manufacturer will tell you what they know will let your vehicle last beyond their warranty period.
So if the manufacturer recommends against E-15 or E-85, STAY THE HELL AWAY!
If the engine is not designed for ethanol the following issues may arise:
1) Ethanol will entrain water whether from humidity, condensation in your tank, or contamination in the gas station's storage tanks. If there are ferrous (Steel/iron)metals in your fuel system they will rust. Ethanol dissolves many rubber fuel hose materials too and may not play well with things like the O-rings in your injectors. It doesn't provide the same cooling as gas in the chamber and can lead to metallurgic issues with pistons and rings or early valve seat wear.
2) Ethanol will flash to vapor under certain heat and pressure conditions. Basic thermo dynamics say vapors condense, liquids do not--you can go air bound (vapor lock) in your fuel injection system with too much ethanol in certain hot/loaded conditions--happens mostly in older cars, but not unheard of in new vehicles.
So make sure you know what your vehicle is built to accept before you go swallowing the corn farmers bull!